Ours comes in very useful, especially when we have guests. It is nice having two bathrooms and a downstairs loo.
I suffer from IBS and wouldn't even contemplate buying a house with only one bathroom.
Our en-suite has an extractor fan and a window that opens so the steam/smell isn't a problem. All we do is open the en-suite window and close the door from the bedroom.
We use the house bathroom for middle of the night visits as it doesn't wake either of us up. Also the en-suite has a cold tiled floor and the house bathroom is carpeted and is much warmer underfoot. The main bathroom has a bigger shower and also a bath so it gets used most of the time anyway.
I caught a nasty D & V bug from hospital once - DD had had it and passed it on to me. By remaining in the bedroom and en-suite I managed to contain it and neither OH or his mum, who was staying with us at the time, caught it.
Our last house had a two bathrooms, neither of which was en-suite, so I'm not bothered about the second one being en-suite, as long as there is a second bathroom.